Rack and Spur Gear Rack pinions are used for lifting mechanisms (vertical movement), horizontal movement, positioning mechanisms, stoppers and to permit the synchronous rotation of a number of shafts generally industrial machinery. However, they are also used in steering systems to improve the direction of cars. The features of rack and pinion systems in steering are as follows: simple framework, high rigidity, small and lightweight, and excellent responsiveness. With this system, the pinion, installed to the steering shaft, is definitely meshed with a steering rack to transmit rotary motion laterlly (converting it to linear motion) so that you can control the wheel. In addition, rack and pinions are 
utilized for many other purposes, such as playthings and lateral slide gates.
As a mechanical component to transfer rotary into linear motion, gear racks tend to be in comparison to ball screws. There are advantages and disadvantages for using racks instead of ball screws. The advantages of a gear rack are its mechanical simplicity, huge load carrying capacity, no limit to the space, etc. One drawback though may be the backlash. The advantages of a ball screw will be the high precision and lower backlash while its shortcomings are the limit in duration due to deflection.
There are applications where the gear rack is stationary, as the pinion traverses and others where in fact the pinion rotates upon a fixed axis while the gear rack moves. The former is used widely in conveying systems while the latter can be used in extrusion systems and lifting/lowering applications.
To provide many variants of rack and pinion, KHK has various kinds of gear racks in share. If the application takes a long duration requiring multiple equipment racks in series, we’ve racks with the tooth forms properly configured at the ends. These are described as “gear racks with machined ends”. Whenever a gear rack is produced, the tooth cutting process and heat treatment process could cause it to try & walk out true. We are able to control this with special presses & remedial processes.